Analysis of an emulsification process using fractional experimental design

Soy oil-in-water emulsions (30% oil) with soy lecithin as emulsfier (4%) were prepared using a stirred vessel under batch conditions. The effects of 7 process variables (impeller-to-tank diameter ratio, temperature, agitation speed, mode of cooling and also pre-emulsification mixing rate, pre-emulsification mixing time and resting time before emulsification) were studied according to a fractional factorial design 2(7-3). The droplet size distributions of the emulsions were measured and the kinetics of destabilization were monitored during 3 months. In the experimental domain, the mixing rate was found to be the most significant variable affecting both the size distribution and the stability. It was followed by the temperature, and the impeller-to-tank ratio depending on the Sauter mean diameter or the ha half-time of the emulsions. Interaction of the temperature with the agitation speed and with the impeller-to-tank diameter ratio was also observed.